The present invention relates to surgical methods and apparatus for the excision and removal of a wide range of tissues. The invention has application for highly delicate procedures involved in areas such as neuro, spinal, orthopaedic, ophthalmic, dental, gynecological, gastrointestinal, urological, otolaryngological and cardiovascular, as well as other areas of the body requiring great care in the removal of tissue. While the present invention has application in a wide range of procedures, the following disclosure pertains principally to minimally invasive techniques in the orthopaedic or spinal surgical fields.
In the field of spinal surgery, one problem that is frequently diagnosed and treated concerns degeneration or herniation of the intervertebral disc. Structural changes occur in the disc that may be due to excessive loading conditions or to normal degeneration with age. Intervertebral disc problems can be as simple as the chronic low back pain experienced by a large percentage of the population, or as severe as conditions in which the disc tissue is virtually non-functioning. In the past, treatment of the intervertebral disc has required complicated and highly invasive surgical procedures. Frequently, these procedures require some degree of fusion between adjacent vertebra serviced by the affected intervertebral disc.
Within the last decade, techniques for percutaneous discectomies have been developed. One such system is described in the patent to Onik, U.S. Reissue Pat. No. 33,258, and in an article entitled Automated Percutaneous Lumbar Diskectomy, dated 1992 in the "Journal of Advances in Orthopaedic Surgery". In the Onik device, tissue to be removed is drawn by suction into the central bore of an outer cutting sleeve. A pneumatically driven inner cutting sleeve operates as a guillotine to resect the disc material. The disc material is suspended in a saline irrigation fluid which also assists in aspiration of the resected disc material through the inner cutting sleeve.
While the experiences with this and other similar apparatus for percutaneous discectomy has been favorable, there is naturally room for improvements in the method and apparatus for minimally invasive tissue removal. The procedures using these apparatus are less invasive than prior surgical techniques, but there is still a need to reduce the amount of time required to perform the tissue removal in percutaneous discectomy and similar surgeries. Even the prior art systems are only capable of removing about 0.7 grams of tissue in five minutes. Faster tissue removal translates to quicker procedures and reduced invasion and risk of trauma. In addition, as with any procedure involved in cutting body tissue, there remains a risk with present systems for the tissue cutter to resect desirable tissue as opposed to undesirable tissue sought to be removed. Finally, although all surgical techniques involve some trauma to surrounding tissue, there is a clear need to reduce even further the amount of trauma associated with a percutaneous procedure as contemplated by the present invention.
At present, the state of the art tissue removal systems generally involve the use of motorized pneumatically driven guillotine or rotary type cutters. One problem with these systems is that tissue is often tom, rather than sliced cleanly. With rotary cutters, the tissue has a tendency to become "spooled" or wound around the cutter or drive shaft, thereby clogging or stalling the cutter. These systems also incorporate a gravity fed saline infusion to provide irrigation fluid at the cutting end. The flow of irrigation fluid is controlled manually by varying the height of the fluid source. In the absence of a controllable fluid source, these prior systems require a significant supply of irrigation fluid in order to have enough fluid available for a given procedure. Moreover, these prior systems provide aspiration vacuum by way of a peristaltic or diaphragmatic pump. These prior vacuum systems are often inefficient at drawing tissue into the cutting opening and can be susceptible to clogging as too much tissue is drawn into the cutting port. Inefficiencies in the irrigation and aspiration of the prior art devices often limit the tissue removal capacity so that often the prior devices cannot remove enough tissue to reduce disc herniation, for example, and the associated pain to the patient.
These features of the prior systems lead to inherent limitations in the ability to remove tissue and the speed of the tissue removal. The present invention addresses these and other problems of the prior art devices to greatly advance the field of minimally invasive percutaneous tissue removal.
While the focus of the present description is on spinal or orthopaedic applications, similar tissue removal apparatus and methods can be applied to tissue removal at other sensitive or delicate sites. One example is in the field of neurosurgery, and specifically removal of tumors, blood clots, lesions, aneurysms or membranes. Prior art devices have been generally ineffective in neurosurgery applications. Other examples of broader use of the present invention is in the urological field for removal of the prostate, gynecological surgery for removal of ovaries and lesions, gastrointestinal surgery for removal of the gallbladder and kidney/gall stones, cardiovascular procedures for removal of plaque, and ophthalmology for treatment of cataracts.